diff --git a/core/modules/language/language.admin.inc b/core/modules/language/language.admin.inc
index 1904a62..a29fb3e 100644
--- a/core/modules/language/language.admin.inc
+++ b/core/modules/language/language.admin.inc
@@ -583,7 +583,10 @@ function language_negotiation_configure_form_submit($form, &$form_state) {
   language_types_set($configurable);
 
   // Clear the block's cache to change the block name when there is only one
-  drupal_container()->get('plugin.manager.block')->clearCachedDefinitions();
+  // Invalidate the block cache to update custom block-based derivatives.
+  if (module_exists('block')) {
+    drupal_container()->get('plugin.manager.block')->clearCachedDefinitions();
+  }
   // $block_manager = new BlockManager(array('Drupal\language\Plugin\Derivative\LanguageBlock'));
   // $block_manager->clearCachedDefinitions();